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191.
K. Stucki S.K. Solanki I. Rüedi J.O. Stenflo A. Brković U. Schühle K. Wilhelm M.C.E. Huber 《Space Science Reviews》1999,87(1-2):315-318
We analyze SUMER spectra of 14 lines belonging to 12 ions, obtained on both sides of the boundary of polar coronal holes as
well as at other locations along the limb. We compare line intensities, shifts and widths in coronal holes with values obtained
in the quiet Sun. We find that with increasing formation temperature, spectral lines show an increasingly stronger blueshift
in coronal holes relative to the quiet Sun at an equal heliospheric angle. The width of the lines is generally larger (by
a few km/s) inside the coronal hole. Intensity measurements show the presence of the coronal hole in Ne VIII lines as well
as in Fe XII, with evidence for a slightly enhanced emission in polar coronal holes for lines formed below 105 K.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
192.
G. Paschmann F. Melzner R. Frenzel H. Vaith P. Parigger U. Pagel O. H. Bauer G. Haerendel W. Baumjohann N. Scopke R. B. Torbert B. Briggs J. Chan K. Lynch K. Morey J. M. Quinn D. Simpson C. Young C. E. Mcilwain W. Fillius S. S. Kerr R. Mahieu E. C. Whipple 《Space Science Reviews》1997,79(1-2):233-269
The Electron Drift Instrument (EDI) measures the drift of a weak beam of test electrons that, when emitted in certain directions, return to the spacecraft after one or more gyrations. This drift is related to the electric field and the gradient in the magnetic field, and these quantities can, by use of different electron energies, be determined separately. As a by-product, the magnetic field strength is also measured. The present paper describes the scientific objectives, the experimental method, and the technical realization of the various elements of the instrument. 相似文献
193.
J. P. Henry U. G. Briel 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1993,13(12):191-198
The combination of the large effective area and the very low internal background of the ROSAT Position Sensitive Proportional Counter provides an extremely sensitive instrument for the study of diffuse X-ray sources. In this paper we review new results on the X-ray structure of nearby clusters as measured with ROSAT. Substructure is a common feature in these objects. Such structure provides evidence that clusters have formed relatively recently through mergers of relatively large subunits. This behavior is predicted by hierarchical formation theories in a dense universe. 相似文献
194.
Geeta Vichare Ankush Bhaskar Gauri Datar Anil Raghav K.U. Nair C. Selvaraj M. Ananthi A.K. Sinha M. Paranjape T. Gawade C.P. Anil Kumar C. Panneerselvam S. Sathishkumar S. Gurubaran 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(10):2555-2568
Recently, equatorial secondary cosmic ray observatory has been established at Equatorial Geophysical Research Laboratory (EGRL), Tirunelveli, (Geographic Coordinates: 8.71°N, 77.76°E), to study secondary cosmic rays (SCR) produced due to the interaction of primary cosmic rays with the Earth’s atmosphere. EGRL is a regional center of Indian Institute of Geomagnetism (IIG), located near the equator in the Southern part of India. Two NaI(Tl) scintillation detectors are installed inside the temperature controlled environment. One detector is cylindrical in shape of size 7.62?cm?×?7.62?cm and another one is rectangular cuboid of 10.16?cm?×?10.16?cm?×?40.64?cm size. Besides NaI(Tl) detectors, various other research facilities such as the Geomagnetic observatory, Medium Frequency Radar System, Digital Ionosonde, All-sky airglow imager, Atmospheric electricity laboratory to measure the near-Earth atmospheric electric fields are also available at EGRL. With the accessibility of multi- instrument facilities, the objective is set to understand the relationship between SCR and various atmospheric and ionospheric processes, during space weather and terrestrial events.For gamma-ray spectroscopy, it is important to test the performance of the NaI(Tl) scintillation detectors and to calibrate the gamma-ray spectrum in terms of energy. The present article describes the details of the experimental setup installed near the equator to study cosmic rays, along with the performance testing and calibration of the detectors under various conditions. A systematic shift in the gain is observed with varying temperature of the detector system. It is found that the detector’s response to the variations in the temperature is not just linear or non-linear type, but it depends on the history of the variation, indicating temperature hysteresis effects on NaI detector and PMT system. This signifies the importance of isothermal environment while studying SCR flux using NaI(Tl) detectors, especially for the experiments conducted during daytime such as solar eclipses etc. 相似文献
195.
196.
J. Gorosabel A. de Ugarte Postigo A.J. Castro-Tirado I. Agudo M. Jelínek S. Leon T. Augusteijn J.P.U. Fynbo M.J. Michałowski D. Xu P. Ferrero D.A. Kann A. LLorente M. Bremer J.-M. Winters C.C. Thöne J. Cepa 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
We present the preliminary results of the recent Hα narrow-band imaging carried out for NGC 2770 with the Gran Telescopio Canarias (GTC) equipped with OSIRIS. We put the polarization measurements reported in Gorosabel et al. (2010) for SN 2007uy and SN 2008D in the context of the morphological information inferred from the Hα imaging. We estimated the orientation of the interstellar polarization (ISP) at the position of SN 2007uy and, most interestingly, at the site of SN 2008D which has been subject of an intensive debate due to its possible connection with Gamma-Ray Bursts (GRBs). The Hα imaging reveals a clumpy interstellar medium (ISM) composed of hundreds of compact emitting regions, for which we determined their sizes. The derived size for the Hα emitting region coincident with SN 2008D is consistent with the ISM cell size limits imposed by Gorosabel et al. (2010) based on millimetric data. A deeper data analysis is under way and will be published elsewhere. This article represents the first attempt to study the site of a possible GRB-like event combining millimetric, polarimetric and narrow-band data. 相似文献
197.
D.O. Demir U. Dogan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
This paper reports on the estimation of changes of a GPS-based crustal deformation field as function of the observing session duration. This investigation was carried out on the Marmara Continuous GPS Network (Marmara region) by using GPS data collected on a set of 10 stations during the period 2002.50–2005.47 The GPS observations were processed in the ITRF 2005 reference frame using Bernese v5.0 software. 相似文献
198.
高能束流(High Energy Density Beam)加工技术包含了以激光束、电
子束和等离子弧为热源对材料或构件进行特种加工的各类工艺方法.高能束流焊(或高能密度焊)是指焊接功率密度比通常的氩弧焊(TIG、MIG)或CO2气体保护焊高的一类焊接方法.严格地讲,焊接能量和焊接功率密度是2个不同的概念,但二者具有相关性. 相似文献
199.
U. Weinbach S. Schön 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Processing data from Global Navigation Satellite Systems (GNSS) always requires time synchronization between transmitter and receiver clocks. Due to the limited stability of the receiver’s internal oscillator, the offset of the receiver clock with respect to the system time has to be estimated for every observation epoch or eliminated by processing differences between simultaneous observations. If, in contrast, the internal oscillator of the receiver is replaced by a stable atomic clock one can try to model the receiver clock offset, instead of estimating it on an epoch-by-epoch basis. In view of the progress made in the field of high-precision frequency standards we will investigate the technical requirements for GNSS receiver clock modeling at the carrier phase level and analyze its impact on the precision of the position estimates. 相似文献
200.
R. Duffard K. Kumar S. Pirrotta M. Salatti M. Kubínyi U. Derz R.M.G. Armytage S. Arloth L. Donati A. Duricic J. Flahaut S. Hempel A. Pollinger S. Poulsen 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
We propose a dual-rendezvous mission, targeting near-Earth asteroids, including sample-return. The mission, Asteroid Sampling Mission (ASM), consists of two parts: (i) flyby and remote sensing of a Q-type asteroid, and (ii) sampling of a V-type asteroid. The targeted undifferentiated Q-type are found mainly in the near-Earth space, and to this date have not been the target of a space mission. We have chosen, for our sampling target, an asteroid from the basaltic class (V-type), as asteroids in this class exhibit spectral signatures that resemble those of the well-studied Howardite–Eucrite–Diogenite (HED) meteorite suite. With this mission, we expect to answer specific questions about the links between differentiated meteorites and asteroids, as well as gain further insight into the broader issues of early Solar System (SS) evolution and the formation of terrestrial planets. To achieve the mission, we designed a spacecraft with a dry mass of less than 3 tonnes that uses electric propulsion with a solar-electric power supply of 15 kW at 1 Astronomical Unit (AU). The mission includes a series of remote sensing instruments, envisages landing of the whole spacecraft on the sampling target, and employs an innovative sampling mechanism. Launch is foreseen to occur in 2018, as the designed timetable, and the mission would last about 10 years, bringing back a 150 g subsurface sample within a small re-entry capsule. This paper is a work presented at the 2008 Summer School Alpbach,“Sample return from the Moon, asteroids and comets” organized by the Aeronautics and Space Agency of the Austrian Research Promotion Agency. It is co-sponsored by ESA and the national space authorities of its Member and Co-operating States, with the support of the International Space Science Institute and Austrospace. 相似文献